One of the life-threatening complications of hyperemesis gravidarum is Wernicke's encephalopathy, the main etiological factor of which is a lack of thiamine (vitamin B1). Most frequently Wernicke's encephalopathy is found among persons suffering from excessive drinking. The aim of the report was to present a case of Wernicke's encephalopathy induced by hyperemesis gravidarum. The course of the disease, clinical signs, diagnostics, treatment and its results are presented. Also a review of the literature on Wernicke's encephalopathy secondary to hyperemesis gravidarum is introduced.